The subject invention concerns an engraving head for engraving gravure or intaglio printing cylinders and other pinting devices and also a sensing stylus sleeve structure and collet for use in such an engraving head.
Electronically controlled mechanical engraving machines, some of which have become known under their trade name "Klischograph," are used for engraving intaglio or rotogravure cylinders. They include an engraving head, or typically several engraving heads located side by side in parallel to a longitudinal axis of the printing cylinder.
Each engraving head has an engraving stylus and a sensing organ or stylus mounted on a common fixture. That fixture can be placed at the printing cylinder for applying the sensing organ or stylus at a predetermined pressure to the printing cylinder surface.
Up and down movement of the engraving stylus is generated by a control signal derived from an image signal produced by scanning a master. A raster signal which determines raster width is superimposed on the image signal. The continuously oscillating engraving stylus cuts into the surface of the gravure or intaglio cylinder pursuant to that control signal, so that raster cells or wells are cut which vary in depth and cross-section or cell volume in accordance with tone value.
Prints made with printing cylinders engraved by such known methods have shown a striated pattern consisting of stripes of differing color values.
As seen relative to the printing cylinder, these stripes extend in the longitudinal axis thereof. In Eurpose, this phenomenon has become known as "Jalousieeffekt"; that is, a "venetian blind effect." This kind of striated pattern effect is caused by periodically occurring unevenness of the cylinder surface or deviations from the geometrically exact cylinder form, which affect the cutting and thereby the formation of the raster cells.